About half of a total population in Japan, eyes become presbyopia at 40 years old or higher, and most of eye disorders are associated with advancing age.
Under such circumstances, presbyopia is diagnosed by subjective inspection, and quantitative evaluation has not been conducted. Further, since it is difficult to grasp specific progress of presbyopia, presbyopia has not appropriately been medical treated.
For these reasons, quantitative evaluation of presbyopia is desired.
A cause of presbyopia is stiffening denaturation of protein in crystalline lens and following reduction of accommodation capability caused by the stiffened crystalline lens by advancing age.
Therefore, if it is possible to measure elasticity of a crystalline lens, quantitative diagnosis becomes possible.
As methods for measuring characteristics of eyes, research on methods using Raman scattering or stimulated Brillouin scattering is conducted.
According to the method using Raman scattering, stiffness of a crystalline lens and a state of progress of cataract are obtained from an amount of moisture in a crystalline lens.
According to the method using stimulated Brillouin scattering, an elasticity state of a corneae and a crystalline lens by a confocal optical system are obtained.
There is proposed an optical inspection apparatus for irradiating a front portion of an eye ball of a test subject with laser light, and measuring a state of an eye of the test subject from conditions of generated scattering light (Japanese Patent Application Laid-open No. S58-206718 and Japanese Patent Application Laid-open No. H6-217939).
Japanese Patent Application Laid-open No. S58-206718 proposes an eye ball opacity diagnostic apparatus for collecting emitted laser light at one point in an eye ball, receiving generated laser scattering light by a photoelectric conversion element to obtain a time correlation function, and calculating a diameter of protein.
Japanese Patent Application Laid-open No. H6-217939 proposes an ophthalmology measuring apparatus for irradiating an anterior segment of an eye ball with laser light, receiving scattering light from protein molecule or cell existing in aqueous humor in anterior chamber, receiving scattering light from corneae, and quantitatively obtaining protein concentration or cell density in aqueous humor in anterior chamber, and a degree of corneal opacity.